Incinerator-gas turbine cycle



1969 J. H. FERNANDES IHCINERATOR-GAS TURBINE CYCLE Filed April 4, 1968 NW. .10... o o o INVENTOR. JOHN H. FERNANDES QM 02W A T TOENE Y 3,473,331 INCINERATOR-GAS TURBINE CYCLE John H. Fernandes, Windsor, Conn., assignor to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed Apr. 4, 1968, Ser. No. 718,774 Int. Cl. F01n 3/02; B01d 45/10; F23g 3/00 US. Cl. 60--59 2 Claims ABSTRACT OF THE DISCLOSURE An incinerator the exhaust gas of which first passes in heat exchange relationship with compressed air, a portion of it is then recirculated back to the upper portion of the incinerator, and the remainder of the exhaust gases then pass through air pollution control equipment such as a wet scrubber where the gases are cleaned. The hot compressed air is used as the motive fluid to drive a gas turbine.

BACKGROUND OF THE INVENTION The disposal of refuse by burning it in an incinerator has been common for a long time. With the growing concern over air pollution, various methods of removing impurities from the combustion gases have been recently introduced. One of the methods used for cleaning the gases is to pass them through a wet scrubber, where the foreign particles combine with the water, which water is thereafter removed from the gas stream. In a conventional incinerator, high excess air is required to obtain complete combustion. This requires large fan sizes for the incinerator, and also requires wet scrubbers of considerable size to handle the large volume of exhaust gases. Also, a considerable amount of water is needed for the wet scrubber in order to reduce the temperature to a level where standard air pollution control equipment, fans and stacks, can handle the combustion gases. In a system of this type the quantities used of both air and water are enormous, these being in the range of about five pounds of air and two pounds of water for every pound of refuse burned. This invention suggests alternate solutions which would reduce the air and water requirement appreciably and would also generate by-product power.

SUMMARY OF THE INVENTION The system of my invention incorporates an incinerator for burning refuse whereby the exhaust gases therefrom first pass in heat exchange relationship with compressed air, a portion of the exhaust gases are thereafter recirculated back to the upper portion of the incinerator, and the remainder of the exhaust gases then pass through the air pollution control equipment where the gases are cleaned. The hot compressed air is used as the motive fluid in driving a gas turbine.

BRIEF DESCRIPTION OF THE DRAWING The figure is a schematic representation of an incinerator-gas turbine arrangement constructed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Looking now to the drawing, numeral 10 depicts an incinerator furnace in which refuse is burned. The hot combustion gases are discharged from the incinerator through upper outlet opening 12. These gases then flow through heat exchanger 14, where they give up heat to another fluid, prior to entering the wet scrubber 16. The gases are scrubbed and cleaned in scrubber 16, and are then exhausted to the atmosphere with substantially all of the impurities removed therefrom.

A gas recirculation duct 18 is connected to the exhaust duct intermediate the heat exchanger 14 and the wet scrubnited States Patent 3,473,331 Patented Oct. 21, 1969 ice ber 16. By means of fan 20, cooled gases are withdrawn from the exhaust duct and introduced into the upper portion of the incinerator 10 through ports 22. These ports are constructed so as to introduce the recirculated gases into the upper portion of the incinerator in a highly turbulent manner. This turbulence insures complete combustion of the volatiles, and also reduces the temperature of the gases leaving the furnace to a level that the heat exchanger 14 can easily handle, for example 1500 F. This gas recirculation performs many of the functions overfire secondary air in a conventional incinerator does, such as inducing furnace turbulence and good mixing of the combustion air with the volatiles, so as to insure complete combustion thereof.

Compressed air is supplied to the heat exchanger 14 by compressor 24, through duct 26. After this compressed air is heated, it flows through duct 28 to gas turbine 30. After expanding through the turbine 30, the air is exhausted through line 34. As an alternative, in some instances it might be of benefit to use the turbine exhaust as combustion air for the incinerator. This might permit elimination of the forced air draft fan. The gas turbine 30 not only drives the compressor 24, but also generator 32, with the power generated thus being used to run the auxiliaries at the incinerator site, or for any other suitable use. In passing through the heat exchanger, the compressed air removes heat from the flue gas while increasing in temperature to approximately 1200 F.

Positioned in the duct 28 between the heat exchanger 14 and gas turbine 30 is a damper 36. This device is used to control the turbine output, While insuring sufiicient air flow through the heat exchanger to guarantee approximately 600 F. exit gas temperature to the wet scrubber, which is the desired maximum temperature this equipment can handle. When an increase in heat exchange air flow or a reduction in auxiliary equipment power requirements take place, the damper 36 is partially opened, relieving some of the hot high pressure air to the atmosphere and balancing the energy requirements imposed on the turbine by the compressor and other auxiliary equipment such as the combustion air fan for the incinerator and the gas recirculation fan 20.

From the above, it can be seen that an efiicient combination incinerator and gas turbine arrangement has been provided in accordance with my invention. In place of the more conventional air dilution and water quenching systems, it incorporates the use of a gas to air heat exchanger. It further incorporates the use of gas recirculation to cool the combustion gases leaving the incinerator to an acceptable 1500 F. before entering the heat exchanger. With the proposed system, requirements of quenching water and excess air have been reduced to a minimum.

The foregoing description relates to what is considered to be the preferred embodiment of the invention.

I claim:

1. In combination, an incinerator for burning refuse therein, a first duct connected to the incinerator through which the hot combustion gases are exhausted, a heat exchanger positioned in the first duct, an air compressor, a second duct connecting the compressor to the heat exchanger, so that compressed air passes in heat exchange relationship with the hot combustion gases from the incinerator, a turbine, third duct means connecting the air side of the heat exchanger to the turbine, so that the hon, compressed air can be used as the motive fluid in driving the turbine, gas cleaning equipment positioned in the first duct downstream of the heat exchanger for cleaning the combustion gases, and fourth duct means having an inlet connected to the first duct downstream of the heat exchanger, and an outlet connected to the upper portion of the incinerator, through which gases can be recirculated back to the incinerator.

3 4 2. The combination set forth in claim 1, including 2,561,717 7/1951 Vicard 11049 damper means positioned in the third duct means, which 3,358,413 12/1967 Kalika.

damper means can be actuated so as to pass the hot compressed air either to atmosphere or to the turbine. CARLTON CROYLE, Prlmary EXamlner 5 ALLAN D. HERRMAN, Assistant Examiner US. Cl. X.R.

References Cited UNITED STATES PATENTS 1,860,366 5/1932 Lucke 11049 55-222, 238; 110-8 2,379,452 7/1945 Nettelet a1. 

